IntercontinentalExchange Group Inc. plans to sell as much as 30% of Euronext NV before the operator of the Paris and Amsterdam exchanges goes public this year, three people with knowledge of the matter said.

Twitter Inc., the social-networking company that has seen its shares soar since debuting on the New York Stock Exchange last month, was downgraded by Macquarie Capital, which said the stock has gone “too far, too fast.”